The present invention relates to a fuel cell system.
In recent years, electric vehicles and so-called hybrid vehicles have come into practical use. Electric vehicles use electricity as a drive power source to avoid contributing to global warming caused by exhaust. Hybrid vehicles use a motor to drive the drive wheels when starting the vehicle or in low speed ranges and uses an engine (combustion engine) to drive the drive wheels at middle and high speed ranges to lower fuel consumption and reduce exhaust. Electric vehicles that use fuel cells in lieu of batteries as a power source (fuel cell vehicles) have also come into practical use. Fuel cell systems installed in fuel cell vehicles generate electromotive power by supplying hydrogen and air (oxygen) to the fuel cells and causing an electrochemical reaction. The reaction between hydrogen and oxygen produces water. Thus, the exhaust contains a large amount of water. A gas-liquid separator separates the water from the exhaust. The exhaust that is free from water (air off-gas) is discharged from an exhaust passage, and the water is discharged out of the system through, for example, an external exhaust valve.
When the vehicle travels outdoors, as long as the water, which is contained in a tank, is discharged little by little as the vehicle travels, this should not cause any problems. However, when a large amount of water is discharged, this will soak the road or the like and is therefore not preferable. When the vehicle is an indoor-operated vehicle or a forklift, which is operated in a building and goes back and forth between indoor and outdoor locations, the discharge of water from the tank at an indoor location will wet the floor and is therefore not preferable.
Japanese Laid-Open Patent Publication No. 2007-141475 discloses a generated water atomizing device that atomizes the water generated in the fuel cell and discharges the atomized water into the atmosphere. The generated water atomizing device includes an electric drain pump that draws in water from a tank and pressurizes the water that has been drawn in. The water ejected from the drain pump passes through a minute nozzle and is sprayed out of an ejection port. This releases atomized water out of the vehicle. Japanese Laid-Open Patent Publication No. 2009-26498 discloses a generated water atomizing device that includes a nozzle, which discharges generated water, and an air pipe, which surrounds the nozzle. In this device, high-temperature air, which is pressurized by an air compressor, is supplied to the air pipe to atomize the generated water discharged from the nozzle. Such devices diffuse the water that is released into the atmosphere and prevents the road or floor from being made wet.
However, in a fuel cell system using the generated water atomizing device described in Japanese Laid-Open Patent Publication No. 2007-141475, the drain pump must be used to pressurize and atomize water. Thus, the generated water atomizing device described in Japanese Laid-Open Patent Publication No. 2007-141475 requires energy to drive the drain pump and space for installing the drain pump. Further, the drain pump is a movable component and thus has limited durability. Further, additional cost is necessary for installing the drain pump.